An image forming apparatus is used to form an image on a sheet. The image forming apparatus may include a developing device and a heating element, such as a power supply unit. There is a possibility that a toner stored in the developing device bonds together to become a lump of toner due to a thermal effect of a heating element on the developing device. Accordingly, an image forming apparatus is required to be capable of suppressing the thermal effect of the heating element on the developing device.